1. Field of the Invention
The present invention relates to camera systems for use in vehicles, and, more particularly, to camera systems for use in parking of vehicles.
2. Description of the Related Art
Nissan has developed a driver assistance system called “Nissan Around View Monitor” which employs four ultra-wide high-resolution cameras mounted in the front, rear and both sides of the vehicle to provide a bird's eye view of the vehicle's surroundings. All those images are processed and displayed in real time on a dash-mounted screen, giving drivers a 360 degree view of obstacles surrounding the vehicle which they may want to avoid hitting. Shifting the car into reverse or drive alternates between a view of the front or rear. Drivers are able to toggle the left, front and right views when performing a particularly tricky parallel parking maneuver. The first application of Nissan's “Around View Monitor” in the United States is in the Infiniti EX35 model.
Mapping is a technique used by robots and vehicles to build up a map within an unknown environment. This is not as straightforward as it might sound due to inherent uncertainties in discerning the robot's relative movement from its various sensors. A system for mapping road surfaces may include high-end LIDAR, GPS and Inertial Measurement Unit (IMU) sensors. The system may produce a two-dimensional surface image of ground reflectivity with five centimeter resolution of the road surface.
Other known systems focus on generating bird's eye views of urban and rural terrains by use of cameras mounted on either aircraft or satellites. The most common approach is pushbroom mosaicing, which works well for applications wherein the desired viewpoint of the final mosaic is close to the original viewpoint.
Some commercial offerings, such as Google's “Street View” or Microsoft's “Street Side”, create static maps of urban scenes. The focus in these systems is on providing views of the urban city similar to what an automobile passenger or pedestrian might see moving around the same city. The differences in perspective between the captured and final images are small if any and all processing can be done offline.
Other systems have been proposed that generate maps using sparse feature representations, sometimes referred to as landmarks. In particular, several attempts at vSLAM (visual simultaneous localization and mapping) have been developed and demonstrated, primarily in indoor environments that use camera systems to create feature based maps. In general, these feature-based maps are unusable by a human attempting to localize himself or his vehicle.
Forward-looking automotive cameras are used in various applications including night vision assistance, lane detection, lane departure warning, lane keeping, and road sign detection. In the future, such cameras will be standard in upper class vehicles. Backward-facing cameras are already used as a visual aid for backing up and may be required in the future for backover avoidance.
Various approaches to parking assistance exist. These approaches have in common that sonar is used as the main sensor. The advantage of sonar is that it is inexpensive. The disadvantage of sonar is that sonar measurements are noisy and inaccurate, which sometimes leads to false system behavior. Existing systems issue a visual and/or audible warning to the driver before a collision with an object. Future systems will assist the driver by operating the steering (i.e., semi-autonomous parking) or steering plus gas/brakes (i.e., fully autonomous parking).
BMW has presented a camera-based system for parking assistance using motion-stereo. This system requires additional sideward-facing cameras in order to detect the parking area.
What is neither disclosed nor suggested by the prior art is a method for utilizing a forward-facing camera and/or a backward-facing camera in providing a driver with an overhead view for assistance in parallel parking.